JP2806643B2 - Bar code reader - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a bar code reading method in which a light beam is repeatedly deflected along a predetermined scanning pattern, and the deflected light beam is transmitted through a transmission type diffraction hologram means to be diffracted toward a bar code reading area. Related to the device.

[0002]

2. Description of the Related Art In recent years, information management systems using barcodes are being introduced not only in POS (Point of Seals) systems but also in fields such as OA (Office Automation) and FA (Factory Automation). Referring to FIG. 11, the appearance of a conventional stationary bar code reader is schematically shown and its housing 10 is shown.
A bar code reading window 12 made of transparent glass or the like is provided on a part of the upper wall surface of the device. Barcode reading window 12
A barcode reading area (three-dimensional area) 14 shown as a hatched area is set on the upper side, and a laser beam L is emitted from the barcode reading window 12 toward the barcode reading area 14 as a light beam. The laser beam L is repeatedly deflected along a predetermined scanning pattern, and such laser beam deflection is
This is performed by a light beam deflection optical system (not shown) provided therein. The light beam deflecting optical system is composed of, for example, a polygon mirror, a reflecting mirror, and the like, and various scanning patterns can be obtained by appropriately designing the reflection angle of the reflecting surface of the polygon mirror and the arrangement of the reflecting mirror. it can.

Referring to FIG. 12, an example of such a scanning pattern is indicated generally by the reference numeral 16, which is conveniently drawn on the top surface of the bar code reading window 12. The scanning pattern 16 is composed of line segments 16a, 16b, 16c, 16d, 16e and 16f crossing each other, and the laser beam L
A, 16b, 16c, 16d, 16e and 16f are sequentially and repeatedly deflected. Accordingly, the laser beam L is also deflected in the bar code reading area 14 along a scanning pattern similar to the scanning pattern 16 shown in FIG. 12, and if an imaginary screen 18 is arranged in the bar code reading area 14, As shown in FIG. 13, a scanning pattern 16 similar to the scanning pattern 16 shown in FIG. In addition,
The scanning pattern 16 shown in FIG. 13 is obtained by viewing the screen 18 from above.

Needless to say, in order to read a barcode, a barcode (not shown) attached to an article or a commodity is passed through a barcode reading area 14,
At this time, the bar code is a line segment 1 forming a scanning pattern.
It can be scanned with a laser beam L deflected along any of 6a, 16b, 16c, 16d, 16e and 16f. A part of the reflected scattered light obtained by scanning the barcode is returned to the barcode reader along the emission path of the laser beam L, and is detected as barcode information. In this case, in order to read the barcode information, the barcode needs to be completely scanned with the laser beam L, and the scanning with the laser beam L is performed for the purpose of completely scanning such a barcode. That is, the light is deflected along the pattern 16. Further, in order to decode a bar code, bar code information having a large S / N ratio, that is, reflected scattered light having a large intensity when scanning the bar code is required. About 200 to 45 in area
It must be squeezed to 0 μm. Conversely,
The deflection area of the laser beam L narrowed to such a beam diameter is set as a barcode reading area. An optical element such as a convex lens is used to stop down the beam diameter of the laser beam L.

[0005] Each line segment 16a, 1
In order to make the complete scanning of the bar code by the laser beam L deflected along 6b, 16c, 16d, 16e, and 16f uniform, it is necessary to make the intersection angles of these line segments approximately equal. In the example of the scanning pattern 16 shown in FIG. 13, the intersection angle is 60 °. Therefore, as is apparent from FIG. 12, the dimensions of the barcode reading window 12 need to be widened so that the entire scanning pattern 16 can be captured, and accordingly, the size of the housing 10 is also adjusted accordingly. Become. In short, the entire conventional barcode reader has a relatively bulky configuration.

[0006] Therefore, by applying a transmission type diffraction hologram element having a special diffraction characteristic to a bar code reading window, the bar code reading window is expanded and reduced, thereby reducing the overall configuration of the bar code reading device. Has been proposed. A bar code reader of this type is shown in a plan view in FIG. 14, and the vertical width (in FIG. 14) of the housing 10 'and the bar code reading window 12' is the housing 10 of the bar code reader shown in FIG.
And the barcode reading window 12 is reduced in length. This is because the scanning pattern 16 'to be deflected by the laser beam may be in a form in which the scanning pattern 16 shown in FIG. 12 is crushed in the vertical direction (in FIG. 14). However, in the bar code reading device shown in FIG.
2 'includes a line segment 16a' forming a scanning pattern 16 ';
16b ', 16c', 16d ', 16e' and 16
A strip-shaped transmission diffraction hologram element (not shown) is applied along f ', and the diffraction laser beam diffracted by the transmission diffraction hologram element is scanned in a bar code reading area by a scanning pattern 16 as shown in FIG. Will be drawn. That is, the scanning pattern 16 '
Of the line segments forming the line segments 16a ', 16c', 1
This is because the transmission type diffraction hologram element applied to 6d 'and 16f' is given a special diffraction characteristic which causes the deflection trajectory of the laser beam to be deflected along it. For example, a laser beam deflected along the line segment 16a 'is diffracted along the line segment 16a in the bar code reading area by the corresponding transmission type diffraction hologram element.

Referring to FIG. 15, a general transmission type diffraction is shown.
An example of creating a hologram element is shown in the figure.
Reference numeral 20 denotes, for example, a photosensitive emulsion on a transparent film substrate.
Shows a recording medium formed by applying
Assumes a three-dimensional rectangular coordinate system xyz with a coordinate origin at the center of
And the recording medium 20 is located in the xy plane.
I do. Reference in the zy plane of this three-dimensional rectangular coordinate system xyz
The light source 22 and the object light source 24 are sandwiched between the y-axis.
When arranged, both light sources 22 and 24 emit light.
Interference fringes are formed on the recording medium 20 by the interference of the generated spherical waves.
Created and recorded. This recording medium 36 is developed / fixed.
The transmission type diffraction hologram with diffraction grating fringes
The gram element is obtained. Referring to FIG.
Transmission diffractive hologram element is designated by reference numeral 20 '.
The transmission type diffraction hologram element 20 'is shown in FIG.
Assuming a three-dimensional rectangular coordinate system xyz similar to 5 and its yz
Laser beam source 22 'as a reproduction light source in the plane
And the laser beam emitted from the₁, L
_TwoAnd L_ThreeDeflected along the x-axis as shown by
When transmitted through the diffraction hologram element 20 ',
The beam is L₁', L _Two'And L_Three′
Diffracted off-axis, but its transmitted laser beam
The deflection trajectory of the system is parallel to the x-axis (note that FIG.
Where x 'and y' are the x and y axes, respectively.
Indicates the projection axis). In short, in the example shown above, diffraction
The deflection direction of the laser beam is not turned.

On the other hand, referring to FIG. 17, there is shown an example in which a transmission type diffraction hologram element for turning the direction of deflection of a diffracted laser beam, that is, a special diffraction characteristic, is shown. The same three-dimensional coordinate system xyz as that of FIG. 17, the reference light source 22 and the object light source 24 are y
(in the example of FIG. 17, the positive side) z one side of the x-axis from the plane disposed displaced position, the creation method of FIG. 17 in this respect is different from the creating of Figure 15. These two light sources 22
And 24, the interference fringes are formed and recorded on the recording medium 20 by the interference of the spherical waves generated from the recording medium 2.
Obtaining a transmission type diffraction hologram element having diffraction grating fringes by developing / fixing 0 is the same as in the case of FIG. Referring to FIG. 18, such a transmission diffraction hologram element is indicated by reference numeral 20 ″, and a three-dimensional orthogonal coordinate system xyz similar to FIG. for Figure 15 and by placing the laser beam source 22 'as a reproduction light source in the same manner as in the yz plane, the laser beam emitted therefrom in the x-axis as indicated by L _1, L ₂ and L ₃ When is deflected to transmit transmission-type diffraction hologram element 20 'along, transmitted laser beam L _1', L ₂ 'but is diffracted so deviates from the x-axis as shown by and L _3', the transmitted laser The deflection trajectory of the beam is turned in the counterclockwise direction differently from the case of FIG.
And y 'denote the x-axis and y-axis projection axes, respectively). When such a transmission diffraction hologram element is used in the bar code reader of FIG. 14, even if the laser beam is deflected along the scanning pattern 16 'on the bar code reading window 12', the diffraction laser beam will The scanning pattern 16 can be drawn in the code reading area.

The reason why the transmission type diffraction hologram element obtained by the manufacturing method shown in FIG. 17 has a diffraction characteristic for rotating a laser beam is briefly described. The interference fringes recorded on the transmission type diffraction hologram element are as follows. Is gradually increased toward the positive side of the x-axis, and the laser beam from the laser beam source 22 ′ shifted from the reference light source 22 to the yz plane side is further diffracted on the positive side of the x-axis. Is to be affected. That is, the laser beam L passing through the side of the largest spatial frequency of the interference fringes
Diffraction effect of ₃ is the largest, the diffraction effect of the laser beam L ₁ passing through the smallest side of the spatial frequency of the fringe is the smallest, the deflection trajectory of the order transmitted laser beam 18
Will be turned as shown in FIG.

[0010]

By the way, in FIG. 18, when the laser beam source 22 'is further shifted to the negative side of the x-axis, the turning effect of the deflection trajectory of the diffracted laser beam is further increased. However, the farther the laser beam source 22 'is from the reference light source 22, the farther the laser beam source 22' is from the Bragg condition, and the more wavefront aberration is apparent. Therefore, the laser beam generation source 22 ′ cannot be largely shifted from the reference light generation source 22. Needless to say, if the value deviates greatly from the Bragg condition, the intensity of the diffracted laser beam is weakened, which hinders bar code reading. When the wavefront aberration becomes apparent, the beam diameter of the diffracted laser beam becomes uneven as shown in FIG. In addition,
In FIG. 19, the beam diameters of the laser beams L ₁ , L ₂ and L ₃ transmitted through the transmission type diffraction hologram element shown in FIG. 18 are exaggerated, and the smallest side of the spatial frequency of the interference fringes is shown. Although the beam diameter of the transmitted laser beam L ₁ ′ is hardly reduced, the aperture effect of the laser beam L ₃ ′ transmitted on the side having the largest spatial frequency of the interference fringes is maximized. In short, since the laser beam generation source 22 'cannot be shifted from the reference light generation source 22 by a large amount, it cannot be expected to reduce the vertical width of the bar code reader shown in FIG. Accordingly, an object of the present invention is a bar code reading apparatus which repeatedly deflects a light beam along a predetermined scanning pattern and transmits the deflected light beam through a transmission type diffraction hologram means to diffract it toward a bar code reading area. Accordingly, it is an object of the present invention to provide a bar code reader which can be further reduced in size without causing the above-described problems of the Bragg condition and the wavefront aberration.

[0011]

According to the present invention, a light beam is repeatedly deflected along a predetermined scanning pattern, and the deflected light beam is transmitted through a transmission type diffraction hologram means. In a bar code reader for diffracting light toward a bar code reading area, the transmission type diffraction hologram means comprises at least two-stage transmission type diffraction hologram elements, and each transmission type diffraction hologram element has a polarized light beam transmitted therethrough. bar diffraction characteristics as to pivot the deflection trajectory of given characterized in that each of the transmission-type diffraction hologram element of at least two-tiered are superimposed so as to pivot the deflection trajectory of the deflected light beam in the same direction Code reader
Provided. Also, according to the present invention, the light beam is deflected.
Deflecting means for deflecting light, and deflecting light deflected by the deflecting means.
And a transmission type diffraction means for transmitting and diffracting the beam.
The transmission-type diffracting means adjusts the polarization of the transmitted polarized light beam.
At least two sheets having diffraction characteristics for rotating a direction locus
Wherein the transmission type diffraction elements of
Transmission diffractive elements mutually deviate the polarization of the transmitted deflected light beam.
Direction trajectories can be overlapped so that they turn in the same direction.
An optical scanning device is provided.

[0012]

As is apparent from the above configuration, in the bar code reader according to the present invention, the polarized laser beam is transmitted through at least two transmission diffraction hologram elements forming transmission diffraction hologram means. And the deflected laser beam is sequentially diffracted by at least two-stage transmission type diffraction hologram elements so that the deflection trajectory can be turned in the same direction. Therefore, the Bragg condition problem and the wavefront aberration problem for each transmission type diffraction hologram element. It is possible to obtain a large effect of turning the deflection trajectory of the diffracted laser beam without making the diffraction visible.

[0013]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Next, an embodiment of a bar code reader according to the present invention will be described with reference to FIGS. Referring first to FIGS. 1 and 2, an example of a transmission type diffraction hologram means 26 which can be used in a bar code reader according to the present invention is indicated by reference numeral 26. The transmission diffraction hologram elements 26a and 26b have the same diffraction characteristics as those of the transmission diffraction hologram element 20 ″ shown in FIG. The spatial frequency of each of 26a and 26b gradually increases toward the positive side of the x-axis of the three-dimensional coordinate system assumed on the surface, but a point to be noted here is that
The three-dimensional coordinate system assumed on each surface of the transmission type diffraction hologram elements 26a and 26b is zy relative to each other.
That is, the relationship is such that the rotation is performed by 180 ° in the plane. In short, the transmission type diffraction hologram element 26a
Are superimposed on the transmission diffraction hologram element 26b such that the densest side of the interference fringe is directed to the sparsest side of the transmission diffraction hologram element 26b, and as shown in FIG. Glued. In this embodiment, the transmission type diffraction hologram elements 26a and 26a
6b are also matched to each other (i.e., the same diffraction characteristics), at which point both transmissive diffractive hologram elements are identical to each other, but as will be apparent from the above description, to each other. From the aligned relationship, they are superposed in a 180 ° rotationally displaced relationship.

The diffraction characteristic of the transmission type diffraction hologram means 26 is obtained by multiplying the individual diffraction characteristics of the transmission diffraction hologram elements 26a and 26b which are stacked in two stages as described below. The diffraction characteristics of the transmission diffraction hologram element 26a are the same as those described with reference to FIG. 18, and the diffraction characteristics of the transmission diffraction hologram element 26b are, as shown in FIG. °
Diffraction characteristics obtained when rotationally displaced. In short, FIG. 3 is the same as FIG. 18 observed from the back of the paper. In FIG. 18, the laser beam is deflected along the x-axis toward the positive side, whereas FIG.
In, the laser beam is deflected along the x-axis toward its negative side, but the diffraction characteristics of the laser beam itself are the same.

Here, the transmission type diffraction hologram means 26
Diffracted through the transmission type diffraction hologram element 26a
The apparent light source of a diffracted laser beam
And its apparent light source is at position P as shown in FIG.₁Or
Position P_TwoThrough position P_ThreeMove up to. FIG.
In order to avoid complicating the drawing, the transmission diffraction
Program element 26a is omitted, but enters there
Deflected laser beam L₁, L_TwoAnd L_ThreeAnd those
Diffraction laser beam L₁', L_Two'And L_Three'In FIG.
Is the same as that shown in FIG. As shown in FIG.
The beam L₁', L_Two'And L_Three′ Actual light source
Is a ray arranged in the yz plane as described in FIG.
The beam sources 22 ', but their apparent
The upper light sources are at position P₁, P_TwoAnd position P_ThreeDistributed to
Will be placed. Therefore, the laser beam source
The laser beam from 22 'is directed to its positive side along the x-axis.
Once deflected, the apparent appearance of the diffracted laser beam
The light source is located at position P in the yz plane. ₁From position P_TwoThrough the position
P_ThreeIt can be considered as a moving light source that moves to

This means that the transmission type diffraction hologram means 2
6 to the transmission type diffraction hologram element 26b.
The laser beam is located at position P₁From position P_TwoRank through
Place P _ThreeIt is obtained from a moving light source that moves to
Referring to FIG._TwoThrough position P_ThreeMove to
Laser beam source to transmit diffraction hologram element 2
6b (note that FIG. 5 shows a transparent
Incident on the over-shaped diffraction hologram element 26b)
The laser beam is LP₁, LP_TwoAnd LP_Three
And from the laser beam source 22 'in FIG.
Laser incident on over-shaped diffraction hologram element 26a
Beam L₁, L_TwoAnd L_ThreeAnd their diffractive laser beads
Mu L₁', L_Two'And L_Three′ Is also shown for reference
I have. As is clear from FIG.₁The light source in
Laser beam LP emitted from₁Is the light from the light source 22 '.
The beam L₁At the same location as₁Is light
Because it is above source 22 ', its diffractive laser beam
Mu LP₁'Is the diffraction laser beam L₁'Diffraction angle
Greater than the position P₁Emitted from the light source at
Laser beam LP incident on the origin_TwoIs from the light source 22 '
Laser beam L heading to the origin_TwoAnd its diffraction
The Beam LP_Two'Is also the diffracted laser beam L_TwoMatches'
Then position P_ThreeBeam L emitted from a light source at
P_ThreeIs the laser beam L from the light source 22 '_ThreeIn the same place as
Incident, but at position P_ThreeIs located below the light source 22 '.
First, the diffracted laser beam LP_Three′ Is a diffraction laser beam
Mu L_Three′ Is further diffracted in the negative direction of the y-axis.

[0017] Thus, as shown in FIG. 6, the laser beam L ₁ to be deflected toward the positive side along the and x-axis is emitted to the transmission type diffraction hologram unit 26 from the laser beam source 22 ', L ₂ and L ₃ are subjected to the respective diffraction actions of the transmission type diffraction hologram elements 26 a and 26 _b to become diffracted laser beams LP ₁ ′, LP ₂ ′ and LP ₃ ′. In this case, the vehicle can be turned further. When such a transmission type diffraction hologram having a large swirling effect is used in a bar code reader of the type shown in FIGS. 11 and 12, the size thereof is reduced.
4 can be achieved. Referring to FIG. 7, a bar code reader using the transmission type diffraction hologram means as described above is shown as a plan view,
The vertical width (in FIG. 7) of the housing 10 "and the bar code reading window 12" is the housing 10 'and the bar code reading window 12' of the bar code reader shown in FIG.
Is further reduced as compared to the vertical width. This is because, for the scanning pattern 16 "in which the laser beam is to be deflected, the scanning pattern 16 'of FIG.
This is because it may be in a further crushed form. In short, the line segments 16a ", 16b", 16c ", 16d", 16 forming the scanning pattern 16 "of such a form.
Line segments 16b ", 16c", and 1 "of e" and 16f "
Since the deflection trajectory of the laser beam deflected along 6d "and 16f 'can be largely swiveled by the transmission type diffraction hologram element means of the type described above, the scanning pattern as shown in FIG. 1
6 can be obtained. Here, it should be noted that a laser beam can be incident on each of the transmission diffraction hologram elements 26a and 26b of the transmission diffraction hologram means 25 without greatly deviating from the Bragg condition. The above-described wavefront aberration problem can be solved according to the present embodiment as described later.

Referring to FIG. 8, the beam diameters of the laser beams L ₁ , L ₂ and L ₃ transmitted through the transmission type diffraction hologram means 26 shown in FIG. 6 and the diffracted laser beams LP ₁ ′, LP ₂ ′. And LP ₃ ′ are exaggerated, and the laser beam L ₁ is
As is most is transmitted through the large side of the spatial frequency for small side at Moreover transmission diffraction hologram element 26b of its most spatial frequencies relative to 6a, the laser beam L ₂ for transmissive diffraction hologram elements 26a and 26b The laser beam L ₃ is transmitted at the point of the spatial frequency having an intermediate magnitude between them, and the transmission diffraction hologram element
a is transmitted on the side of the largest spatial frequency with respect to a and on the side of the smallest spatial frequency with respect to the transmission type diffraction hologram element 26b. Accordingly, the beam diameters of the diffracted laser beams LP ₁ ′, LP ₂ ′ and LP ₃ ′ are narrowed down to the same extent, and the problem of wavefront aberration can be solved. This is because the transmission type diffraction hologram elements 26a and 26b have the same spatial frequency characteristics in the present embodiment.

In the embodiment described above, the transmission type diffraction hologram elements 26a and 26b are both assumed to have the same spatial frequency characteristics. However, the transmission type diffraction hologram elements 26a and 26b are provided with different spatial frequency characteristics. Even in this case, a large turning effect can be obtained on the deflection trajectory of the deflected laser beam. Also, in this case, the above-mentioned wavefront aberration problem is not solved, but can be reduced. This is because, for example, a laser beam transmitted through one transmission-type diffraction hologram element on the side of the lowest spatial frequency is transmitted through the other transmission-type diffraction hologram element on the side of the highest spatial frequency. This is because they are the same.

Referring to FIGS. 9 and 10, there is shown an embodiment in which the present invention is applied to a hand-held bar code reader. The hand-held bar code reader includes a housing 28 for accommodating a light beam deflection optical system and the like. And a handle portion 30 extending from the bottom surface of the rear end of the housing 28. A pair of upper and lower transmission diffraction hologram means 32 and 34 forming a bar code reading window are provided in the front opening of the housing 28, and these transmission diffraction hologram means 32 and 34 are of the type shown in FIG. Is used. The light beam deflecting optical system housed in the housing 28 includes a polygon mirror 36, which is hexagonal in this embodiment. For example, a semiconductor laser (not shown) is disposed between the polygon mirror 36 and the barcode reading window, and a laser beam is emitted from the semiconductor laser toward the polygon mirror 36 which is rotated, for example, counterclockwise. Anti slopes with two reflection angle are alternately arranged in the port Rigonmira 36, while the laser beam reflected by the reflecting surface having a reflection angle along a transmission type diffraction hologram unit 32 in its lateral deflection The laser beam reflected and reflected by the reflection having the other reflection angle deflects the transmission diffraction hologram means 34 along its lateral direction, whereby the transmission diffraction hologram means 32 and 34 The beams will be incident alternately. The deflection trajectory of the laser beam transmitted and diffracted through each of the transmission type diffraction hologram means 32 and 34 is rotated, whereby a scanning pattern 38 is drawn by the diffraction laser in front of the bar code reading window,
This scanning pattern 38 is composed of line segments 38a and 38b that cross each other. When the bar code is emitted from the reading window Moreover barcode with the laser beam with the laser beam is deflected along the line 38a and 38b is Ru are scanned <br/>, detecting the reflected scattered light as a bar code information Is done. The handle 30 is provided with a switch 30a. When the switch 30a is turned "on" by an operator's finger, a barcode reading operation is performed by a hand-held barcode reader.

A point to be noted here is that the transmission diffraction hologram elements of the two-stage stack constituting the transmission diffraction hologram means 32 and 34 have the same spatial frequency. That is, if the transmission diffraction hologram element of two-stage stacked the same spatial frequency are given, as apparent from FIG. 6, the laser beam L ₂ which is caused to enter the coordinate origin from the laser beam source 22 'transmission The diffraction hologram means 26 is made to go straight, and thus the scanning pattern 3
8 is formed on the front side of the bar code reading window as clearly shown in FIG. This is an important feature for hand-held bar code readers. That is, in a hand-held bar code reader, it is natural that the front side of the bar code reading window is the target direction for reading the bar code. This is because the reading window and the polygon mirror can be arranged in a state where they are aligned with each other. That is, when a bar code reading window is formed by the transmission type diffraction hologram element 20 ″ as shown in FIG.
As to form the bar code reading window on the front side in the scan pattern should place the port re Gonmira at positions displaced from each other transversely relative to the bar code reading window, and size of the housing along with this Ru Oh <br/> is no otherwise.

In the above-described embodiment, the transmission type diffraction hologram means is formed from two-stage transmission type diffraction hologram elements. However, the transmission type diffraction hologram means is formed from three or more transmission type diffraction hologram elements. Alternatively, the turning effect of the deflection trajectory of the deflection laser beam may be further enhanced. In this case, it is preferable that transmission-type diffraction hologram elements be superposed on even-numbered stages rather than superposed on odd-numbered stages. This is because the wavefront aberration problem can be reduced or eliminated when transmission-type diffraction hologram elements are superposed evenly. Further, in the above-described embodiment, the transmission diffraction hologram element is formed by bonding the transmission diffraction hologram elements individually formed to each other, but a plurality of transmission diffraction hologram elements are sequentially formed on the same transparent film substrate. It is also possible. That is, the first on the transparent film substrate
That is, after the transmission diffraction hologram element of the second stage is formed, a photosensitive emulsion is further coated thereon to form the transmission diffraction hologram element of the second stage. Furthermore, in the above-described embodiment, the two-stage transmission type diffraction hologram elements are assumed to have the same spatial frequency, but it is not always necessary to give the transmission type diffraction hologram elements the same spatial frequency.

In the embodiment shown in FIGS. 9 and 10, a polygon mirror is used as the light beam deflecting means. However, other light beam deflecting means such as a galvano mirror or a diffraction hologram disk for deflecting the light beam may be used. Is also possible.

[0024]

As is apparent from the above configuration, according to the present invention, the turning effect of the deflection trajectory of the deflected laser beam can be enhanced without the Bragg condition problem and the wavefront aberration problem. It is possible to obtain a bar code reader having a compact configuration.

[Brief description of the drawings]

FIG. 1 is a schematic perspective view showing a transmission diffraction hologram means used in a bar code reader according to the present invention.

FIG. 2 is a side view showing transmission diffraction hologram elements constituting the transmission diffraction hologram means of FIG.

FIG. 3 shows a second embodiment of the transmission type diffraction hologram means of FIG.
It is a perspective view explaining one diffraction characteristic of the transmission diffraction hologram element of a step stack.

FIG. 4 shows a second embodiment of the transmission diffraction hologram means of FIG.
It is a perspective view explaining the other diffraction characteristic of the transmission type diffraction hologram element of a step stack.

FIG. 5 is a perspective view for explaining the diffraction characteristics of the transmission diffraction hologram means of FIG. 1 together with the diffraction characteristics of the transmission diffraction hologram elements of a two-stage stack.

FIG. 6 is a perspective view showing diffraction characteristics of the transmission type diffraction hologram means of FIG. 1;

FIG. 7 is a plan view of a stationary barcode reader according to the present invention using the transmission diffraction hologram means of FIG. 1;

8 is a schematic diagram illustrating the wavefront aberration characteristics of the transmission type diffraction hologram means of FIG.

FIG. 9 is a perspective view of a hand-held bar code reader according to the present invention using the transmission type diffraction hologram means of FIG. 1;

FIG. 10 is a side view of the hand-held bar code reader of FIG. 9;

FIG. 11 is a schematic side view illustrating a conventional stationary bar code reader.

FIG. 12 is a plan view of the stationary bar code reader of FIG. 11;

FIG. 13 is a plan view showing a scanning pattern in a bar code reading area of the stationary bar code reader of FIG.

FIG. 14 is a schematic plan view showing another type of the conventional stationary barcode information reader.

FIG. 15 is a perspective view illustrating an example of creating a general transmission diffraction hologram element.

FIG. 16 is a perspective view illustrating diffraction characteristics of the transmission diffraction hologram element created in FIG.

FIG. 17 is a perspective view illustrating an example of forming a transmission type diffraction hologram element used in the stationary barcode reader of FIG. 14;

FIG. 18 is a perspective view illustrating the diffraction characteristics of the transmission type diffraction hologram element created in FIG. 17;

FIG. 19 is a schematic diagram illustrating wavefront aberration characteristics of the transmission diffraction hologram element of FIG. 18;

[Explanation of symbols]

 10.10'.10 "housing 12.12'.12" barcode reading window 14.barcode reading area 16.16'.16 ".scanning pattern 18.screen 20.recording medium 20'.20" .. Transmission diffraction hologram element 22 Reference light source 22 'Laser beam generation source 26 Transmission diffraction hologram means 26a / 26b Transmission diffraction hologram element 28 Housing 30 Handle part 32/34 Transmission diffraction hologram means 38 ... Scanning pattern

────────────────────────────────────────────────── (5) References JP-A-63-316018 (JP, A) JP-A-63-180825 (JP, U) (58) Fields investigated (Int. Cl. ⁶ , DB name) G06K 7/12 G02B 5/32 G02B 27/09 G06K 7/10

Claims (3)

(57) [Claims] 1. A bar code reading device that deflects light beams causes repeatedly along a light beam in a predetermined scanning pattern deflected allowed transmission to the transmission diffraction hologram hand stage diffracting toward the bar code reading area, wherein given transmission diffraction hologram hand stages at least two-tiered in the transmission diffraction hologram essential hydride Rannahli, diffraction characteristics as to pivot the deflection trajectory of the deflected light beam transmitted therethrough in each transmission diffraction hologram element A bar code reader, wherein the at least two transmission diffractive hologram elements are superimposed so as to rotate the deflection trajectory of the deflected light beam in the same direction. In the bar code reading apparatus according to claim 1, from said transmission diffraction hologram element of two-stage stacked has a <br/> same diffraction characteristics from each other, yet aligned mutually aligned relationship A barcode reader characterized by being superposed in a 180 ° rotationally displaced relationship. 3. A deflecting means for deflecting a light beam;
The deflected light beam deflected by the deflector is transmitted and diffracted.
Transmission type diffraction means, wherein the transmission type diffraction means comprises
A circuit that turns the deflection trajectory of the transmitted deflected light beam.
At least two transmissive diffraction elements having folding characteristics
And the plurality of transmission diffraction elements are mutually joined.
The deflection trajectory of the transmitted deflected light beam turns in the same direction.
Optical scanning characterized by being superimposed to rotate
apparatus.